We have examined the correlation between heat tolerance and small heat shock protein (sHSP) expression under heat stress conditions in potato (Solanum tuberosum L.). The relative heat tolerance of nine potato cultivars grown under greenhouse conditions was determined using the electrolyte leakage assay (ELA), a standard quantitative assay for heat tolerance. Three cultivars differing in heat tolerance were selected and designated as heat-tolerant (‘Laura’), moderately sensitive (‘Liseta’) and heat-sensitive (‘Agria’) genotypes. The expression of cytosolic HSP18 and chloroplast HSP21 was analyzed at the protein level in the leaves of selected cultivars, both ex vitro- and in vitro-grown, after heat stress or control treatment. Immunoblot analysis revealed heat-induced HSP18 and HSP21 expression in all examined genotypes. A similar pattern of examined sHSP expression was observed ex vitro and in vitro: heat-tolerant ‘Laura’ accumulated higher levels of both HSP18 and HSP21 compared to heat-sensitive ‘Liseta’ and ‘Agria’. Our results indicate that ELA combined with immunoblot analysis of sHSP accumulation under HS conditions, might be considered as a reliable procedure in screening potato genotypes for heat tolerance. To our knowledge, this is the first study where sHSP expression between ex vitro- and in vitro-grown potato plants was compared

Potato eukaryotic elongation factor 1A comprises multiple isoforms, some of which are heat-inducible or heat-upregulated and might be important in alleviating adverse effects of heat stress on plant productivity. Heat stress substantially reduces crop productivity worldwide, and will become more severe due to global warming. Identification of proteins involved in heat stress response may help develop varieties for heat tolerance. Eukaryotic elongation factor 1A (eEF1A) is a cytosolic, multifunctional protein that plays a central role in the elongation phase of translation. Some of the non-canonical eEF1A activities might be important in developing plant heat-stress tolerance. In this study, we investigated effects of heat stress (HS) on eEF1A expression at the protein level in potato, a highly heat vulnerable crop. Our results from both the controlled environment and the field have shown that potato eEF1A is a heat-inducible protein of 49.2-kDa with multiple isoforms (5-8). Increase in eEF1A abundance under HS can be mainly attributed to 2-3 basic polypeptides/isoforms. A significant correlation between eEF1A abundance and the potato productivity in the field was observed in two extremely hot years 2011 and 2012. Genomic Southern blot analysis indicated the existence of multiple genes encoding eEF1A in potato. Identification, isolation and utilization of heat-inducible eEF1A genes might be helpful for the development of the heat-tolerant varieties.

A two-year field trial was conducted to study the effects of biohumus, biofertiliser, and soil conditioner application on spelt grain yield in different regions (plain, hilly, and mountainous regions) in Serbia. An analysis of economic efficiency indicators of spelt production in organic farming systems was also performed. The field experiment had a randomised complete block design with three replicates in each of the three regions. One winter spelt cultivar was also studied. The largest differences in spelt yield compared to control were found in the plain region in the biohumus + biofertiliser treatment (28.0%) and the hilly region in the organic fertiliser + zeolite treatment (28.8%). The differences in grain yield between control and treatment conditions in the mountain region were insignificant. Analysis of the economic effects of organic spelt production found a significantly lower gross margin in treatments with expensive organic fertilisers (3955.05 and 1104.75 € ha–1) than the control (5094.31 and 1833.85 € ha–1), leading to the conclusion that their application was not economically justified despite the increases in grain yield. The highest production costs (3569.71 € ha–1) were observed in treatments in the hilly region, resulting in the lowest benefit-cost ratio (0.1), while the greatest benefit-cost ratio was recorded in treatments in the mountainous region (2.1). Following the economic analysis results, a significant negative correlation between the benefit-cost ratio and the total production costs (r= –0.91**) was determined and a positive correlation between the gross margin and grain yield (r=0.66*). These results lead to the conclusion that the management strategy of spelt production in organic farming systems should be harmonised with the soil and agro-ecological characteristics of the region and directed at decreasing the costs and share of external inputs. In this case, organic spelt production can be economically profitable. Highlights - Organic fertilisers and soil conditioners affect spelt grain yield. - The analysis of the economic effects of organic spelt production concluded that fertiliser application was not economically justified despite the increases in grain yield. - Treatments in the plain region displayed the best production results compared to mountain region treatments, but these did not have the best benefit-cost ratio. - Knowledge of production costs is an important element in improving the economic efficiency of organic farming systems.

At the micropropagation laboratory of the Potato Research Centre in Gucha, the following five virus-free in vitro potato cultivars are produced: 'Desiree', 'Kennebec', 'Agria', 'Cleopatra' and 'Sinora'. Acclimatized and rooted plants were transplanted and grown in the three production systems: 1) the aeroponic system, 2) the substrate system, and 3) a combination of the substrate and aeroponic systems. The results obtained indicate that the cultivation system exerts a significant effect on the number and the total yield of potato mini-tubers. In the aeroponic production system, 4.08 times as many mini-tubers were produced compared to the number of mini-tubers produced in the substrate system, whereas 1.29 times as many mini-tubers were produced compared to the number of mini-tubers produced in the combined production system (substrate + aeroponics). The aeroponic mini-tuber production system offers an opportunity to improve the production of seed potatoes in Serbia..